As I've been informed, OpenCL is not supported on Lexa cards (e.g. RX 550) with the latest AMDGPU PRO. Already concerned team is in process to update the release note accordingly.

P.S. Though OpenCL is not supported, RX 550 is compatible with the base driver, hence there is no issue with the installation.

Regards,

So, considering that it's now been roughly 4 months since this issue was reported, and 17.40 is out now and still doesn't work for OpenCL with the RX550 (I've had time to test this now too), I would strongly consider looking into alternatives if you want to use Linux based tools. It's not even clear that the underlying issue is going to be fixed, even if it seems like it must be a fairly simple bug (likely related to the GPU numbering of the RX550, which has cropped up to cause bugs in other places), since the windows OpenCL drivers are fine.